1. Field of the Invention
The instant disclosure relates to a random access memory; in particular, to a high-k metal gate random access memory.
2. Description of Related Art
In the semiconductor industry, the technology associated with dynamic random access memory (DRAM) has been advancing continuously. This technological advancement has lead to size reduction for internal semiconductor components. The size reduction means higher storage density for the memory device. Specially, the internal channel length of the semiconductor components or the gaps in between the components has a decisive impact on component density and the critical dimension. In addition, the critical dimensions of the semiconductor components are limited by the manufacturing process. Taking the existing semiconductor manufacturing process for example, the critical factor that determines the dimensions of the semiconductor components is usually the minimum resolution of the photolithography process.
The minimum resolution will continue to shrink as the semiconductor technology continues to advance. However, there is a limit to which the semiconductor component can be downsized. The reason is during the downsizing process, the required physical and electrical properties of the semiconductor components may be lost due to excessive shrinkage. Taking a memory device as an example, by shrinking its critical dimension, the internal channel of the semiconductor component may be too short. One of the consequences is the overlapping of the bit trapping regions, which can cause errors in reading and/or writing the data. Besides, when the channel is too short, leakage of electricity is more likely to occur for the semiconductor component. Hence, the capacitance for the capacitor of the memory device becomes more difficult to maintain, such that the stored data may be easily lost. Thus, as the semiconductor components becoming increasingly smaller, it is necessary to change the structure of the components to maintain its physical and electrical properties.